Incandescent lamp and method of manufacture



March 22, 1949. E N 2,465,084

INCANDESCENT LAMP AND METHOD OF MANUFACTURE Filed May 14, 1948 Invenkor Ais-Fred Gr'einer",

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Patented Mar. 22, 1949 2,465,084 INCANDESCENT LAMP AND METHOD OF MANUF TUBE Alfred Greiner, Cleveland Heighta,hio, am... to General Electric Company, a corporation of New York Application May 14, 1948, Serial No. 26,989

7 Claims. (01. 176-32) My invention relates to electric incandescent lamps or similar devices and to a method of manufacture thereof. The invention is especially useful for electric incandescent lamps of the miniature type.

Electric incandescent lamps as manufactured at present are generally provided with a separate base member which is either cemented or mechanically afiixed to the glass envelope of the lamp. In addition, the leading-in wires of such lamps are usually sealed through a glass stem or through the glass wall of the lamp envelope, as a result of which especially constructed and relatively expensive types of lead-in wires must be employed in order to obtain an air-tight seal.

It is one object, therefore, of my invention to provide an electric incandescent lamp which will dispense with the basing operations heretofore generally employed in the manufacture of such lamps and which will not require the sealing of the lead-in wires through glass.

Another object of my invention is to provide an electric incandescent lamp of novel and simple construction, and which is relatively inexpensive to manufacture.

Still another object of my invention is to provide a novel method of manufacturing an electric incandescent lamp.

Further objects and advantages of my invention will appear from the following detailed description of a species thereof and from the accompanying drawing in which:

Figs. '1 to illustrate the steps in the manufacture of an electric incandescent lamp according to the invention, Fig. 1 showin a sectional elevation and Fig. 2 a bottom plan view of the two metal parts of the lamp base prior to the joining together thereof; Fig. 3 illustrates the joining of the two metal base parts together; Fig. 4 illustrates the mounting of the lamp filament on the base; Fig. 5 illustrates the sealing of the base and mount assembly to the glass envelope of the lamp; Fig. 6 is an elevation, partly in section, of a completed electric incandescent lamp comprising my invention; and Fig. 7 is a fragmentary section on the line 1-1 of Fig. 6.

Referring to the drawing, the lamp there shown comprises an evacuated glass envelope 1 having a neck portion 2 closed off by a circularly-shaped base or end cap structure 3 comprising a pair of thin metal cap sections 4-5 having flat halfdisc shaped p orti ons 4'-.-5' fusion sealed around their semi-circular peripheries to the rim end of the envelope neck 2, with the diametral edges 6 of the disc halves 4'-5 separated a sli ht (1k.

2 tance apart. The base cap sections 4-! are preferably made of silver-plated iron containing a small percentage of carbon, e. g., .05 per cent, and they are provided with peripheral lip or side wall portions I which fit over the ends of the glass envelope land are fusion sealed to the outer wall surface thereof. As shown in Fig. 6, the rim end of the envelope neck portion 2 is also sealed to the disc halves 4'-5' which thereby constitute, in effect, a portion of the end wall of the envelope itself. The lass envelope I is made of a" suitable low-melting point glass which matches the expansion characteristics of the metal base end cap sections 4-5 and which readily wets and seals thereto. For sealing to silver-plated iron end caps such as are preferably employed, 1 have found a soft lead glass of the following approximate composition to be particularly suitable: v

. Percent s10, 1 45 PhD 35 A1203 2 NazO 3 K20 14 L 1 If desired, the lithium oxide in the above composition may be omitted.

The base can sections 4-5 are formed with terminal contact extensions or flanges 8 which extend straight out from the diametral edges 6 of the disc halves 4'5' and are approximately coextensive therewith. The outer extremities of the terminal contact extensions 8 are bowed outwardly away from one another as indicated at l to form, in effect, a split cylinder extending diametrically across substantially the full diameter of the base end of the lamp. The bowed or curved portions 9 of the terminal contact extensions 0 serve as a convenient means for providing a snap engagement with cooperating spring finger contacts of a lamp socket. As shown. a web of glass l0 fills substantially the entire space between and is sealed to the terminal contact extensions 8 and to the rim end of the envelope neck 2 to thereby hermetically seal the gap between and insulate the two base cap sections 4-5 and to also reinforce the bowed portions 9 of the contact extensions 8 against bending thereof, particularly when engaged by the lamp socket contacts.

Supported from the base structure 3 is a filament mount I l comprising a pair of lead-in wires l2-l3 which are fastened at one end to respective ones of the base cap sections 4-5. In the particular lamp illustrated, the lead-in wires I2-I3 extend through apertured indentations I4 in the half-disc portions 4'-5 of the base cap sections 4-5 and are secured to the latter by metallic fusible material or solder I5-l6 which fills the indentations and hermetically closes the apertures therein 50 as to hermetically seal the envelope I. Inwardly of the lamp envelope, the leadin wires I2-I3 are joined and held in spaced relation by a glass insulating bead I'I fused to the said wires. The inner ends of the lead-in wires I2-I3 are connected to opposite ends of an electric energy translation element or filament I8 such as a coiled or coiled-coil wire of tungsten or other suitable refractory metal.

In manufacturing the lamp according to the preferred method comprising my invention, one of the lead-in. wires of the lamp (wire I2 in the case illustrated) is first suitably secured in place to the base cap section 4 to extend inwardly therefrom, as shown in Fig. 1. The fastening of the lead-in wire I2 to the cap section 4 may be accomplished by inserting it through the aperture in the indentation I4 of the said cap section and securing one end of the wire thereto by a quantity of a suitable metallic fusible material or hard solder I5 having a melting point which is relatively high but below the melting point (960 C.) of the silver plating on the metal cap sections 4-5. For this purpose I prefer to employ a silver solder having a melting point of around BOO-900 C. or thereabouts. Instead of soldering the lead-in wire I2 to the base cap section. 4, it may be secured thereto in any other suitable manner as by welding, for instance, in which case the aperture in the indentation I4 of cap section 4 would be omitted.

The two base cap sections 4-5 are next joined together, as shown in Fig. 3, by a web In of glass insulation to form the base structure 3. In this operation, the two cap sections 4-5 are supported in inverted side-by-side relation with their diametral edges 6-6 adjacent and opposite one another but spaced a slight distance apart (as shown in Fig. 3) and a glass rod I9 inserted and gripped between the outwardly bowed portions 9 of the terminal contact extensions 3 on the cap sections. The glass rod I9 is co-extensive in length with the terminal contact extensions 8 and it is made of a glass composition (preferably the same as the glass of the envelope I) which will readily wet and seal to the silverplated cap sections 4-5. The glass rod I9 is then heated and softened by the application of gas fires 2D to the bowed portions 9 of the extensions 8 on cap sections 4-5 and the latter moved toward one another to press the extensions 8 against opposite sides of the softened glass rod I9, as a result of which the softened glass fiows and is squeezed down between the extensions 8 so as to substantially fill the space therebetween and seal tightly thereto, thus completing the base structure 3 (Fig. 4). The solid web I of glass thus formed between the extensions 8 serves to reinforce and firmly hold them in fixed relation to one another against bending thereof, particularly when engaged by the spring contacts of a lamp socket.

The base structure 3 is provided with a filament mount II as shown in Fig. 4 to form a combination base and mount assembly 2|. The filament mount II may be provided on the base structure 3 by inserting the lead-in wire I3 into the aperture of indentation I4 in the base cap section and sealing a glass insulating bead I 'I around the two lead-in wires I 2-I3 while the 4 latter are held in proper relation with one another. The glass bead I! thus serves to tie the two lead-in wires I2-I3 together in spaced, insulated'relation to each other, with one end of lead-in Wire I3 extending into the indentation I4 in cap section 5 through the aperture thereinr The coiled filament I8 is then connected at its ends, as by clamping or welding, to the inner ends of the two lead-in wires I2-I3 to thereby complete the filament mount II and form the combination base and mount assembly 2| shown in Fig. 4. Instead of building up the filament mount II on the base structure 3 in the manner described above, the entire filament mount II comprising the lead-in wires I2-I3, glass insulating bead I I and filament I8, may be preformed as an entirely separate unit and then suitably fastened in place either on the completed base structure 3, or on the base cap section 4 prior to the joining thereof to the other cap section 5, by soldering the end of lead-in wire I2 to the base cap section 4 within the indentation I4 therein or by spot-welding the end of lead-in Wire I2 to the cap section 4.

The completed base and mount assembly II is then sealed to the rim end of the envelope neck 2 (as shown in Fig. 5) to complete the lamp envelope assembly, except for the final evacuation and seal-off thereof. The sealing of the envelope I to the base and mount assembly 2| may be performed by inserting the neck end 2 of the envelope I within the peripheral lips 1 of the base cap sections 4-5 so as to be surrounded thereby with the rim end of the envelope neck 2 resting of its own weight on the semi-circular portions 4'-5 of. the cap sections 4-5, and then suitably heating the peripheral regions of the base cap sections 4-5 (as by gas fires 22, or by induction heating, or by conduction or radiation from a heated body located adjacent or contacting the cap sections 4-5) to soften the rim end of the glass envelope I as well as the portions of the glass web I0 adjacent the periphery of the base structure 3. The heating is continued until the softened glass rim of the envelope I is thoroughly fused and sealed around its entire circular extent to the lip portions I and semi-circular portions 4-5' of the cap sections 4-5 and to the glass web I0 bridging the gap between the two base cap sections 4-5.

The completed lamp envelope assembly thus formed is then evacuated and sealed-off, and lead-in wire I3 connected to cap section 5, to thereby complete the manufacture of the lamp. The evacuation and sealing-off of the lamp envelope assembly may be performed in the same manner as disclosed in my co-pending application, Pat. #2,449,650, filed October 1, 1947, by supporting the lamp in an inverted position within an exhaust chamber with a pellet of a suitable metallic fusible material or soft solder I6 resting within the as yet unsealed aperture in the indentation I4 of cap section 5, and then evacuating the exhaust chamber and heating and fusing the solder I6 to cause it to flow into and fill the indentation H in cap section 5, thus connecting the lead-in wire I3 to the cap section 5 and closing off the aperture therein to hermetically seal-off the lamp. The solder I6 employed for sealing the aperture in base cap section 5 should have a lower melting point than that of the solder I5 sealing off the aperture in the other base cap section 4 so as to enable the fusion of the solder I6 and therefore the hermetic sealing of the aperture in cap section 5 without softening and affecting in any way the solder seal I! of the aperture in the other cap section 4. For this purpose, I have found a solder composition composed of silver, copper and phosphorus to be very satisfactory for sealing the aperture in the in- The phosphorus in such a solder material has a tendency to act both as a flux and as a getter for the lamp. For the solder used to fasten the lead-in wire l2 to the cap section 4, I prefer to employ a solder material having a melting point below that of the silver plating on the metal base cap sections 4-5 but well above the softening temperature of the glass of which the envelope I is made, so as to assure that the soldered joint between the lead-in wire I! and the cap section 4 will not be afiected during the subsequent sealing of the glass envelope l to the combination base and mount assembly H. For

this purpose, I have found a solder composedv approximately of 50% silver and 50% copper to be particularly satisfactory.

Instead of evacuating and sealing-off the lamp by the chamber exhaust method referred to hereinabove, the lamp may be evacuated through and sealed-off by the tipped-off residue of a conventional glass exhaust tube provided on the envelope assembly and communicating with the interior thereof, as by fusing one end of such an exhaust tube to the portion 4 or 5' of one of the metal base cap sections 4-5 over an aperture therethrough. In such case, both the lead-in wires l2l'3 of the filament mount ll may be secured to the base structure 3 prior to the sealing of the base and mount assembly H to the envelope I.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical device comprising a glass envelope having a tubular open end, a pair of separated thin metal plates sealed at their peripheries to and closing the said envelope end, a web of glass sealed to the said metal plates and envelope end and hermetically closing the gap therebetween, and terminal contact extensions on said plates projecting outwardly therefrom.

2. An electrical device comprising a glass envelope having a tubular open end, a pair of separated thin metal plates sealed at their peripheries to and closing the said envelope end, and a web of glass sealed to the said metal plates and envelope end and hermetically closing the gap therebetween, said metal plates having spaced terminal contact extensions projecting outwardly from their adjacent edges and sealed to opposite sides of the said glass web.

3. An electrical device comprising a glass entary portions bowed outwardly away from each other.

4. An electrical device comprising a glass envelope having a tubular open end, a pair of thin metal half-discs sealed at their peripheries to the said envelope end with their diametral edges separated, and a web of glass sealed to the diametral edge portions of the disc halves and to the envelope end and hermetically closing the gap therebetween, said disc halves having spaced terminal contact extensions projecting outwardly from their diametral edges in slde-by-side interrelation and sealed to opposite sides of the said glass web.

5. An electrical device comprising a glass envelope having a tubular open end, a pair of thin metal half-discs sealed at their peripheries to the said envelope end with their diametral edges separated, and a web of glass sealed to the diametral edge portions of the disc halves and to the envelope end and hermetically closing the gap therebetween, said disc halves having spaced terminal contact extensions approximately 00- extensive with and projecting outwardly from the diametral edges of the disc halves in side-byside interrelation and sealed to opposite sides of the said glass web, the outer end portions of said extensions being bowed outwardly away from each other to define a split cylinder and the glass web substantially filling the space between and reinforcing the said bowed end portions.

6. The method of manufacturing an electric incandescent lamp having a base structure comprising a pair of thin metal half-discs each having a flange extending transversely from and approximately co-extensive with its diametral edge, which method comprises the steps of sealing a glass rod to the flanges of said disc halves to join the disc halves together in spaced relation to form a split disc assembly with the glass of said rod substantially filling the space between the said flanges and forming a glass insulating web therebetween, fastening a filament mount on said split disc assembly, and sealing an open end of a glass lamp envelope to the periphery of said split disc assembly and to the said glass web to hermetically close the gap between the disc halves.

7. The method of manufacturing an electric incandescent lamp having a base structure comprising a pair of thin metal half-discs each having a flange extending transversely from and approximately co-extensive with its diametral edge and bowed outward adjacent its outer edge, which method comprises the steps of fusing a glass rod positioned between and co-extensive with the facing concave sides of said flanges while the said half-discs are held in side-by-side complementary relation with their said flanges upstanding, pressing the flanges against the fused glass rod to seal them to the glass rod and form a glass insulating web substantially filling the space between the said flanges and joining the disc-halves together, fastening a filament mount on the joined disc-halves, and sealing an open end of a glass lamp envelope to the periphery of the joined disc-halves and to the said glass web to hermetically close the gapbetween the disc-halves.

' ALFRED GREINER.

No references cited. 

